US20170162296A1 - High reliability power cables for subsea application - Google Patents
High reliability power cables for subsea application Download PDFInfo
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- US20170162296A1 US20170162296A1 US15/323,695 US201515323695A US2017162296A1 US 20170162296 A1 US20170162296 A1 US 20170162296A1 US 201515323695 A US201515323695 A US 201515323695A US 2017162296 A1 US2017162296 A1 US 2017162296A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/02—Disposition of insulation
- H01B7/0208—Cables with several layers of insulating material
- H01B7/0216—Two layers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/28—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances natural or synthetic rubbers
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J127/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers
- C09J127/02—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
- C09J127/12—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/06—Insulating conductors or cables
- H01B13/14—Insulating conductors or cables by extrusion
- H01B13/141—Insulating conductors or cables by extrusion of two or more insulating layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/06—Insulating conductors or cables
- H01B13/14—Insulating conductors or cables by extrusion
- H01B13/145—Pretreatment or after-treatment
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/06—Insulating conductors or cables
- H01B13/14—Insulating conductors or cables by extrusion
- H01B13/148—Selection of the insulating material therefor
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
- H01B3/441—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from alkenes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/14—Submarine cables
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
- H01B7/1875—Multi-layer sheaths
- H01B7/188—Inter-layer adherence promoting means
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/04—Flexible cables, conductors, or cords, e.g. trailing cables
- H01B7/046—Flexible cables, conductors, or cords, e.g. trailing cables attached to objects sunk in bore holes, e.g. well drilling means, well pumps
Definitions
- Electric submersible pump (ESP) power cables and motor lead extensions (MLE) incorporate high integrity insulation and armor.
- Conventional cables may rely on lead layers to resist high temperatures and pressures, and corrosives in the well fluid. While the lead sheaths provide excellent barrier properties, the regulation of lead metal and its use can results in leaded cables with reduced reliability and lower lifespan.
- the dielectric constant within the unintended micro-voids and gaps is less than that of the surrounding dielectric, allowing the possibility of partial discharges—localized dielectric breakdowns of the insulation.
- Gas-filled micro-voids or packets between the insulation and the conventional lead barrier may also cause barrier layer damage, such as lead barrier rupture during conditions when the cable is rapidly being depressurized or undergoing cyclic pressurization.
- a power cable for an electric submersible pump comprises an electrical conductor in the power cable, an elastomeric insulation layer around the electrical conductor, a fluoroplastic barrier layer around the elastomeric insulation layer, and a bonding layer between the elastomeric insulation layer and the fluoroplastic barrier layer, the bonding layer formulated to prevent a dielectric breakdown of the power cable and a rapid gas decompression breakdown of the power cable.
- ESP electric submersible pump
- An example method includes extruding an elastomeric insulation layer onto one or more components of a power cable for an electric submersible pump (ESP), including at least a conductor, creating an adhesive surface layer on the elastomeric insulation layer, and extruding a fluoroplastic barrier layer onto the adhesive surface to molecularly cross-link with the elastomeric insulation layer.
- ESP electric submersible pump
- Another example method includes extruding an elastomeric insulation layer comprising a fluoroplastic-compatible modified EPDM rubber onto one or more components of a power cable for an electric submersible pump (ESP), including at least a conductor, then preserving the fluoroplastic-compatible modified EPDM rubber from an ambient environment, extruding a fluoro-plastic barrier layer onto the fluoroplastic-compatible modified EPDM rubber, and creating an interface bonding surface between the fluoroplastic-compatible modified EPDM rubber of the elastomeric insulation layer and the fluoroplastic barrier surface.
- ESP electric submersible pump
- FIG. 1 is a diagram of example layers of an example power cable with improved interfacial bonding.
- FIG. 2 is a diagram of an example triple extrusion process for making a power cable with improved interfacial bonding using a fluoroplastic compatible elastomeric insulation layer.
- FIG. 3 is a diagram of an example extrusion process for making a power cable with improved interfacial bonding using a conventional elastomeric insulation layer.
- FIG. 4 is a flow diagram of an example method of making a power cable with improved interfacial bonding using a conventional elastomeric insulation layer.
- FIG. 5 is a flow diagram of an example method of making a power cable with improved interfacial bonding using a fluoroplastic compatible elastomeric insulation layer.
- This disclosure describes high reliability power cables for subsea applications. Since subsea applications provide one of the most challenging environments for cables, the high reliability power cables described herein may also be used for most other applications.
- a tough fluoroplastic barrier layer made to bond well with the insulation layer.
- “Barrier,” as used herein, means that the layer resists an aggressive environment that may expose the power cable to wear, to high temperatures and pressures, and also means that the layer is relatively impermeable to, and inert against, hot and pressurized corrosives in the well fluid, such as dissolved carbon dioxide CO 2 , methane CH 4 , and hydrogen sulfide H 2 S.
- the fluoroplastic barrier layer and its methods of construction provide several advantages. First, the environmental and regulatory issues that accompany using lead metal are avoided.
- the bonding interface between underlying elastomeric insulation and the fluoroplastic barrier is superior to that of conventional lead metal extruded onto the insulation layer.
- PD partial discharge
- the superior bonding interface that avoids the micro-voids and gaps between the insulation layer and the overlying fluoroplastic barrier also eliminates the possibility of the voids trapping gases, which can expand during rapid decompression to damage the power cable.
- FIG. 1 shows an example power cable 100 with an improved bonding interface 102 formed between a fluoroplastic primer-adhesive layer 104 and an insulation layer 106 .
- the improved bonding interface 102 is shown in comparison with conventional micro-voids 150 formed at the interface 152 between a conventional lead barrier layer 154 and a conventional insulation layer 156 .
- power cable 100 also includes motor lead extensions (MLEs) and includes power cables 100 with one or more solid or braided conductors.
- MLEs motor lead extensions
- power cables 100 with one or more solid or braided conductors For clarity, the explanation of layers focuses on layers around a single conductor, used as an example.
- the example power cable 100 may include the following layer components: a conductor 110 , such as copper with a corrosion-resistant coating 112 ; the insulation layer 106 , such as polypropylene, EPR, EPDM, polyimide, or PEEK; the bonding interface 102 , such as the fluoroplastic primer-adhesive layer 104 ; and the fluoroplastic barrier layer 108 .
- the insulation layer 106 may be cured EPDM rubber (ethylene propylene diene monomer), a synthetic elastomeric rubber.
- a jacket layer (not shown), such as EPR & EPDM, nitrile, fluoroplastic, etc., is extruded over the fluoroplastic barrier layer 108 .
- an armor layer (not shown), such as galvanized steel, a Monel alloy, an Inconel alloy, and so forth, may be further extruded or otherwise formed over the jacket layer.
- the example fluoroplastic barrier layer 108 described herein also takes the place of the jacket layer.
- the example fluoroplastic barrier 108 described herein takes the place of both the jacket layer and/or the armor layer, so that no lead metal whatsoever is used in the example power cable 100 .
- Partial discharge (PD) is a localized dielectric breakdown of a small portion of a solid (or fluid) electrical insulation system under high voltage stress, but which does not bridge the entire space or distance between two adjacent conductors.
- micro-voids containing gases introduced during extrusion may be one of the leading causes for the partial discharge (PD) phenomenon.
- the resistance of the power cable to rapid gas decompression may be compromised by the existence of such gas micro-voids or gas packets located at the interface between insulation and barrier.
- barrier layer damage such as lead barrier ruptures during conditions in which the system is rapidly depressurized or undergoing cyclic pressurization.
- the improved bonding interface 102 of the example power cable 100 can prevent these vulnerabilities.
- FIG. 2 shows an example triple extrusion process 200 that can be applied in two passes, for example.
- a primer layer 202 may be preheated by blowing hot air, dry nitrogen, etc., followed by extruding another thicker fluoroplastic barrier layer 210 as the effective impermeable layer on top of this primer layer 202 .
- the primer layer 202 can be a thin fluoroplastic layer that does not interfere with outgassing of cure byproducts of an EPDM insulation layer 204 underneath it during post-curing.
- the example triple extrusion process 200 includes applying the primer layer 202 after application of the insulation layer 204 to a conductor 110 , such as a tie layer coated conductor 110 . Extrusion of the primer layer 202 is followed by a curing process, for example in a steam tube 206 , and a post-curing process 208 . Then, the fluoroplastic barrier layer 210 is applied at a separate cross head 212 .
- the triple extrusion process 200 can be implemented by co-extrusion cross heads 214 , or by separate tandem extrusion steps (not shown).
- the interface between insulation 204 and barrier layers 210 is protected from (not exposed to) the ambient environment, before barrier layer 210 extrusion.
- the enhanced extrusion process 200 utilizes triple extrusion or tandem extrusion and minimizes interfacial contamination of the insulation-barrier interface.
- the example power cable 100 includes an electrical conductor 110 , an elastomeric insulation layer 204 around the electrical conductor 110 , a fluoroplastic barrier layer 210 around the elastomeric insulation layer 204 , and a bonding layer 202 between the elastomeric insulation layer 204 and the fluoroplastic barrier layer 210 .
- the bonding layer 202 is formulated to prevent a dielectric breakdown of the power cable 100 and rapid gas decompression breakdown of the power cable 100 .
- the elastomeric insulation layer 204 may be a cured ethylene propylene diene monomer (EPDM) rubber.
- the elastomeric insulation layer 204 may be a fluoroplastic-compatible modified EPDM rubber.
- the bonding layer 202 may be a fluoroplastic primer-adhesive 202 between the fluoroplastic-compatible modified EPDM rubber 204 and the fluoroplastic barrier layer 210 .
- the bonding layer 202 may include an agent for stripping fluorine atoms from the face of the fluoroplastic barrier layer 210 .
- the agent strips fluorine atoms from the face of the fluoroplastic barrier layer 210 to allow cross-linking bonds to form with the fluoroplastic-compatible modified EPDM rubber 204 .
- the agent may be a metal oxide and a dehydrohalogenating chemical, such as an onium compound, an organo-onium, an amidine, DBU, or DBN.
- DBN is 1,5-Diazabicyclo[4.3.0]non-5-ene, with the compound formula C 7 H 12 N 2 .
- DBN is an amidine base.
- DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene.
- the fluoroplastic barrier layer 210 may be one of the following: a polyvinylidene fluoride fluoroplastic, a polyvinylidene difluoride (PVDF) fluoroplastic, a polyvinyl fluoride (PVF), an ethylene tetrafluoroethylene (ETFE), or a chlorotrifluoroethylene (CTFE).
- the barrier layer 210 may be selected from the polyaryletherketone family such as a polyetherketone (PEK), a polyether ether ketone (PEEK), or a polyetherketone-etherketoneketone (PEKEKK), etc.
- the bonding layer 202 which is the primer or primer-adhesive 202 applied to the fluoroplastic-compatible modified EPDM rubber insulation layer 204 , can be a synthetic rubber fluoropolymer elastomer, a terpolymer of tetrafluoroethylene (TFE) and vinylidene fluoride (VF2) and hexafluoropropylene (HFP), such as VITON (DuPont Performance Elastomers LLC, Wilmington, Del.), or a fluorothermoplastic of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, such as DYNEON THV 500 GZ (3M Company, St. Paul, Minn.).
- TFE tetrafluoroethylene
- VF2 vinylidene fluoride
- HFP hexafluoropropylene
- VITON DuPont Performance Elastomers LLC, Wilmington, Del.
- DYNEON THV 500 GZ 3
- a reactive PVDF or fluoropolymer such as THV (the above fluoroplastic consisting of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride), has excellent chemical and permeation resistance and low flammability and can be formulated into a hydrocarbon elastomer insulation compound such as EPDM/EPR which later reacts and bonds to the fluoropolymer barrier layer 210 applied next (EPR contains only the ethylene and propylene monomers, whereas EPDM also contains a diene monomer).
- THV the above fluoroplastic consisting of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride
- the fluoroplastic barrier layer 210 may include a blocking agent to increase the impermeability of the fluoroplastic barrier layer 210 , such as clay, carbon black, graphene, graphite, talc, mica, silica, or metal particles/nanoparticles, and so forth.
- a blocking agent to increase the impermeability of the fluoroplastic barrier layer 210 , such as clay, carbon black, graphene, graphite, talc, mica, silica, or metal particles/nanoparticles, and so forth.
- the fluoroplastic barrier layer 210 may also assume the role of a jacket layer in the power cable 100 or an outer armor layer of the power cable 100 .
- FIG. 3 shows an example tandem co-extrusion process 300 using an insulation layer 302 that may be a conventional EPDM rubber, for example, over a tie layer 304 on the conductor 110 .
- the example co-extrusion process 300 is followed by curing, e.g., via a steam tube 306 , and post-curing 308 , which is then followed in turn by a surface activation 310 of the insulation layer 302 via plasma activation or electron beam activation, for example.
- the activated EPDM insulation layer 302 may then undergo co-extrusion with an adhesive 312 and the impermeable fluoroplastic barrier layer 314 .
- the co-extrusion steps can be performed via respective co-extrusion cross heads 316 & 318 , or in separate tandem extrusion processes.
- the plasma activation may be weakly ionized oxygen plasma, for example, to activate the surface of the insulation layer 302 .
- the adhesive fluoroplastic layer 312 such as one of the PFA adhesives, can be coextruded with the impermeable fluoroplastic barrier layer 314 , with or without a blocking agent such as graphene nanoparticles, for example, as a filler to further increase the tortuosity of the permeation path for gases and liquids.
- FIG. 4 is a flow diagram of an example method 400 of making an ESP power cable. Operations of the example method 400 are shown as individual blocks.
- an elastomeric insulation layer is extruded onto one or more components of a power cable for an electric submersible pump (ESP), including at least a conductor.
- ESP electric submersible pump
- an adhesive surface layer is created on the elastomeric insulation layer.
- a fluoroplastic barrier layer is extruded onto the adhesive surface to molecularly cross-link with the elastomeric insulation layer.
- the elastomeric insulation layer may be a cured ethylene propylene diene monomer (EPDM) rubber, and creating the adhesive surface layer may include activating a surface layer of the EPDM rubber with a plasma activation or an electron-beam activation.
- EPDM cured ethylene propylene diene monomer
- Creating the adhesive surface layer on the elastomeric insulation layer may further include extruding a fluoroplastic primer or adhesive onto the elastomeric insulation layer prior to extruding the fluoroplastic barrier layer.
- the method 400 may use a triple extrusion process or tandem extrusion processes.
- the fluoroplastic barrier layer may be one of a polyvinylidene fluoride fluoroplastic, a polyvinylidene difluoride (PVDF) fluoroplastic, a polyvinyl fluoride (PVF), an ethylene tetrafluoroethylene (ETFE), or a chlorotrifluoroethylene (CTFE).
- the barrier layer 210 may be selected from the polyaryletherketone family such as a polyetherketone (PEK), a polyether ether ketone (PEEK), or a polyetherketone-etherketoneketone (PEKEKK), etc.
- FIG. 5 is a flow diagram of an example method 500 of making an ESP power cable. Operations of the example method 500 are shown as individual blocks.
- an elastomeric insulation layer comprising a fluoroplastic-compatible modified EPDM rubber is extruded onto one or more components of a power cable for an electric submersible pump (ESP), including at least a conductor.
- ESP electric submersible pump
- the fluoroplastic-compatible modified EPDM rubber is preserved from an ambient environment
- a fluoroplastic barrier layer is extruded onto the fluoroplastic-compatible modified EPDM rubber.
- an interface bonding surface is created between the fluoroplastic-compatible modified EPDM rubber of the elastomeric insulation layer and the fluoroplastic barrier surface.
- the method 500 may further include applying a fluoroplastic primer-adhesive as the interface bonding surface between the fluoroplastic-compatible modified EPDM rubber and the fluoroplastic barrier layer.
- the fluoroplastic primer-adhesive can be selected from the following: a synthetic rubber fluoropolymer elastomer, a terpolymer of tetrafluoroethylene (TFE) and vinylidene fluoride (VF2) and hexafluoropropylene (HFP), or a fluorothermoplastic of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride.
- the method 500 may further include adding an agent to the fluoroplastic primer-adhesive for stripping fluorine atoms from a face of the fluoroplastic barrier layer.
- an agent to the fluoroplastic primer-adhesive for stripping fluorine atoms from a face of the fluoroplastic barrier layer.
- the agent strips fluorine atoms from the face of the fluoroplastic barrier layer to allow molecular cross-linking between the fluoroplastic barrier layer and the fluoroplastic-compatible modified EPDM rubber.
- the agent may be a metal oxide and a dehydrohalogenating chemical, such as an onium compound, an organo-onium, an amidine, DBU, or DBN.
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Abstract
Description
- This patent application claims the benefit of priority to U.S. Provisional Patent Application No. 62/020,888 to Xiang et al., filed Jul. 3, 2014 and incorporated by reference herein in its entirety.
- Electric submersible pump (ESP) power cables and motor lead extensions (MLE) incorporate high integrity insulation and armor. Conventional cables may rely on lead layers to resist high temperatures and pressures, and corrosives in the well fluid. While the lead sheaths provide excellent barrier properties, the regulation of lead metal and its use can results in leaded cables with reduced reliability and lower lifespan.
- In conventional cable-making, lead metal is extruded onto the insulation in its own separate extrusion process. The insulation, however, has already been post-cured and does not bond very significantly with the molten lead. Due to this lack of interfacial bonding and a difference in the coefficient of thermal expansion between these materials, gas-filled micro-voids and impurities carried over from previous post-curing processes are introduced between the conventional insulation layer and the conventional lead sheath.
- The dielectric constant within the unintended micro-voids and gaps is less than that of the surrounding dielectric, allowing the possibility of partial discharges—localized dielectric breakdowns of the insulation.
- Gas-filled micro-voids or packets between the insulation and the conventional lead barrier may also cause barrier layer damage, such as lead barrier rupture during conditions when the cable is rapidly being depressurized or undergoing cyclic pressurization.
- High reliability power cables for subsea application are provided. In an implementation, a power cable for an electric submersible pump (ESP), comprises an electrical conductor in the power cable, an elastomeric insulation layer around the electrical conductor, a fluoroplastic barrier layer around the elastomeric insulation layer, and a bonding layer between the elastomeric insulation layer and the fluoroplastic barrier layer, the bonding layer formulated to prevent a dielectric breakdown of the power cable and a rapid gas decompression breakdown of the power cable. An example method includes extruding an elastomeric insulation layer onto one or more components of a power cable for an electric submersible pump (ESP), including at least a conductor, creating an adhesive surface layer on the elastomeric insulation layer, and extruding a fluoroplastic barrier layer onto the adhesive surface to molecularly cross-link with the elastomeric insulation layer. Another example method includes extruding an elastomeric insulation layer comprising a fluoroplastic-compatible modified EPDM rubber onto one or more components of a power cable for an electric submersible pump (ESP), including at least a conductor, then preserving the fluoroplastic-compatible modified EPDM rubber from an ambient environment, extruding a fluoro-plastic barrier layer onto the fluoroplastic-compatible modified EPDM rubber, and creating an interface bonding surface between the fluoroplastic-compatible modified EPDM rubber of the elastomeric insulation layer and the fluoroplastic barrier surface.
- This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
- Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein.
-
FIG. 1 is a diagram of example layers of an example power cable with improved interfacial bonding. -
FIG. 2 is a diagram of an example triple extrusion process for making a power cable with improved interfacial bonding using a fluoroplastic compatible elastomeric insulation layer. -
FIG. 3 is a diagram of an example extrusion process for making a power cable with improved interfacial bonding using a conventional elastomeric insulation layer. -
FIG. 4 is a flow diagram of an example method of making a power cable with improved interfacial bonding using a conventional elastomeric insulation layer. -
FIG. 5 is a flow diagram of an example method of making a power cable with improved interfacial bonding using a fluoroplastic compatible elastomeric insulation layer. - In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
- This disclosure describes high reliability power cables for subsea applications. Since subsea applications provide one of the most challenging environments for cables, the high reliability power cables described herein may also be used for most other applications.
- In an implementation, the pitfalls of a conventional lead sheath extruded onto an insulation layer in an ESP power cable are overcome with a tough fluoroplastic barrier layer made to bond well with the insulation layer. “Barrier,” as used herein, means that the layer resists an aggressive environment that may expose the power cable to wear, to high temperatures and pressures, and also means that the layer is relatively impermeable to, and inert against, hot and pressurized corrosives in the well fluid, such as dissolved carbon dioxide CO2, methane CH4, and hydrogen sulfide H2S. The fluoroplastic barrier layer and its methods of construction provide several advantages. First, the environmental and regulatory issues that accompany using lead metal are avoided. Second, the bonding interface between underlying elastomeric insulation and the fluoroplastic barrier is superior to that of conventional lead metal extruded onto the insulation layer. This stronger interfacial bonding between the insulation layer and the overlying fluoroplastic barrier, as described herein, prevents formation of unwanted micro-voids and air gaps. These voids and gaps between layers can allow “partial discharge” (PD) dielectric breakdown at high voltage. Third, the superior bonding interface that avoids the micro-voids and gaps between the insulation layer and the overlying fluoroplastic barrier also eliminates the possibility of the voids trapping gases, which can expand during rapid decompression to damage the power cable.
-
FIG. 1 shows anexample power cable 100 with an improvedbonding interface 102 formed between a fluoroplastic primer-adhesive layer 104 and aninsulation layer 106. The improvedbonding interface 102 is shown in comparison with conventional micro-voids 150 formed at theinterface 152 between a conventionallead barrier layer 154 and aconventional insulation layer 156. The example fluoroplastic primer-adhesive layer 104 (“adhesive layer” 104) described herein, in turn, bonds well with an examplefluoroplastic barrier 108 overlying theadhesive layer 104. - The term “power cable” 100, as used herein, also includes motor lead extensions (MLEs) and includes
power cables 100 with one or more solid or braided conductors. For clarity, the explanation of layers focuses on layers around a single conductor, used as an example. - The
example power cable 100 may include the following layer components: aconductor 110, such as copper with a corrosion-resistant coating 112; theinsulation layer 106, such as polypropylene, EPR, EPDM, polyimide, or PEEK; thebonding interface 102, such as the fluoroplastic primer-adhesive layer 104; and thefluoroplastic barrier layer 108. Theinsulation layer 106 may be cured EPDM rubber (ethylene propylene diene monomer), a synthetic elastomeric rubber. - In some implementations, a jacket layer (not shown), such as EPR & EPDM, nitrile, fluoroplastic, etc., is extruded over the
fluoroplastic barrier layer 108. In turn, an armor layer (not shown), such as galvanized steel, a Monel alloy, an Inconel alloy, and so forth, may be further extruded or otherwise formed over the jacket layer. In an implementation, the examplefluoroplastic barrier layer 108 described herein also takes the place of the jacket layer. In an implementation, the examplefluoroplastic barrier 108 described herein takes the place of both the jacket layer and/or the armor layer, so that no lead metal whatsoever is used in theexample power cable 100. - As mentioned above, conventional methods for extruding lead metal onto elastomeric insulation have the vulnerability of a lack of interfacial bonding between the lead metal and the elastomeric insulation, made worse by a difference in their coefficients of thermal expansion. This scenario allows gas-filled voids and micro-defects to form between the conventional insulation layer and the conventional lead barrier sheath.
- Since the dielectric constant of these unintended voids is considerably less than that of the surrounding dielectric, the electric field across the voids is significantly higher than that across an equivalent distance of the dielectric. If the voltage stress across the void is increased above a corona inception voltage for the gas trapped within the void, partial discharge (PD) electrical activity begins to occur. Partial discharge (PD) is a localized dielectric breakdown of a small portion of a solid (or fluid) electrical insulation system under high voltage stress, but which does not bridge the entire space or distance between two adjacent conductors.
- In a similar manner, micro-voids containing gases introduced during extrusion may be one of the leading causes for the partial discharge (PD) phenomenon. The resistance of the power cable to rapid gas decompression may be compromised by the existence of such gas micro-voids or gas packets located at the interface between insulation and barrier. The accumulation of gases at these imperfect interfaces leads to barrier layer damage, such as lead barrier ruptures during conditions in which the system is rapidly depressurized or undergoing cyclic pressurization. The improved
bonding interface 102 of theexample power cable 100 can prevent these vulnerabilities. -
FIG. 2 shows an exampletriple extrusion process 200 that can be applied in two passes, for example. In the second pass, aprimer layer 202 may be preheated by blowing hot air, dry nitrogen, etc., followed by extruding another thickerfluoroplastic barrier layer 210 as the effective impermeable layer on top of thisprimer layer 202. Theprimer layer 202 can be a thin fluoroplastic layer that does not interfere with outgassing of cure byproducts of anEPDM insulation layer 204 underneath it during post-curing. - The example
triple extrusion process 200 includes applying theprimer layer 202 after application of theinsulation layer 204 to aconductor 110, such as a tie layer coatedconductor 110. Extrusion of theprimer layer 202 is followed by a curing process, for example in asteam tube 206, and apost-curing process 208. Then, thefluoroplastic barrier layer 210 is applied at aseparate cross head 212. Thetriple extrusion process 200 can be implemented by co-extrusion cross heads 214, or by separate tandem extrusion steps (not shown). - In an implementation, in order to reduce the effect of surface imperfection introduced during a single pass extrusion process, the interface between
insulation 204 and barrier layers 210 is protected from (not exposed to) the ambient environment, beforebarrier layer 210 extrusion. Theenhanced extrusion process 200 utilizes triple extrusion or tandem extrusion and minimizes interfacial contamination of the insulation-barrier interface. - In an implementation, the
example power cable 100 includes anelectrical conductor 110, anelastomeric insulation layer 204 around theelectrical conductor 110, afluoroplastic barrier layer 210 around theelastomeric insulation layer 204, and abonding layer 202 between theelastomeric insulation layer 204 and thefluoroplastic barrier layer 210. Thebonding layer 202 is formulated to prevent a dielectric breakdown of thepower cable 100 and rapid gas decompression breakdown of thepower cable 100. - The
elastomeric insulation layer 204 may be a cured ethylene propylene diene monomer (EPDM) rubber. For example, theelastomeric insulation layer 204 may be a fluoroplastic-compatible modified EPDM rubber. Thebonding layer 202 may be a fluoroplastic primer-adhesive 202 between the fluoroplastic-compatible modifiedEPDM rubber 204 and thefluoroplastic barrier layer 210. - The
bonding layer 202 may include an agent for stripping fluorine atoms from the face of thefluoroplastic barrier layer 210. When thefluoroplastic barrier layer 210 is extruded to encapsulate the fluoroplastic-compatible modifiedEPDM rubber 204, the agent strips fluorine atoms from the face of thefluoroplastic barrier layer 210 to allow cross-linking bonds to form with the fluoroplastic-compatible modifiedEPDM rubber 204. The agent may be a metal oxide and a dehydrohalogenating chemical, such as an onium compound, an organo-onium, an amidine, DBU, or DBN. Chemically, DBN is 1,5-Diazabicyclo[4.3.0]non-5-ene, with the compound formula C7H12N2. DBN is an amidine base. Chemically, DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene. - The
fluoroplastic barrier layer 210 may be one of the following: a polyvinylidene fluoride fluoroplastic, a polyvinylidene difluoride (PVDF) fluoroplastic, a polyvinyl fluoride (PVF), an ethylene tetrafluoroethylene (ETFE), or a chlorotrifluoroethylene (CTFE). Alternatively thebarrier layer 210 may be selected from the polyaryletherketone family such as a polyetherketone (PEK), a polyether ether ketone (PEEK), or a polyetherketone-etherketoneketone (PEKEKK), etc. - In an implementation, the
bonding layer 202, which is the primer or primer-adhesive 202 applied to the fluoroplastic-compatible modified EPDMrubber insulation layer 204, can be a synthetic rubber fluoropolymer elastomer, a terpolymer of tetrafluoroethylene (TFE) and vinylidene fluoride (VF2) and hexafluoropropylene (HFP), such as VITON (DuPont Performance Elastomers LLC, Wilmington, Del.), or a fluorothermoplastic of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, such asDYNEON THV 500 GZ (3M Company, St. Paul, Minn.). A reactive PVDF or fluoropolymer, such as THV (the above fluoroplastic consisting of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride), has excellent chemical and permeation resistance and low flammability and can be formulated into a hydrocarbon elastomer insulation compound such as EPDM/EPR which later reacts and bonds to thefluoropolymer barrier layer 210 applied next (EPR contains only the ethylene and propylene monomers, whereas EPDM also contains a diene monomer). - The
fluoroplastic barrier layer 210 may include a blocking agent to increase the impermeability of thefluoroplastic barrier layer 210, such as clay, carbon black, graphene, graphite, talc, mica, silica, or metal particles/nanoparticles, and so forth. - In an implementation, the
fluoroplastic barrier layer 210 may also assume the role of a jacket layer in thepower cable 100 or an outer armor layer of thepower cable 100. -
FIG. 3 shows an exampletandem co-extrusion process 300 using aninsulation layer 302 that may be a conventional EPDM rubber, for example, over atie layer 304 on theconductor 110. Theexample co-extrusion process 300 is followed by curing, e.g., via asteam tube 306, and post-curing 308, which is then followed in turn by asurface activation 310 of theinsulation layer 302 via plasma activation or electron beam activation, for example. The activatedEPDM insulation layer 302 may then undergo co-extrusion with an adhesive 312 and the impermeablefluoroplastic barrier layer 314. The co-extrusion steps can be performed via respective co-extrusion cross heads 316 & 318, or in separate tandem extrusion processes. - The plasma activation may be weakly ionized oxygen plasma, for example, to activate the surface of the
insulation layer 302. Theadhesive fluoroplastic layer 312, such as one of the PFA adhesives, can be coextruded with the impermeablefluoroplastic barrier layer 314, with or without a blocking agent such as graphene nanoparticles, for example, as a filler to further increase the tortuosity of the permeation path for gases and liquids. -
FIG. 4 is a flow diagram of anexample method 400 of making an ESP power cable. Operations of theexample method 400 are shown as individual blocks. - At
block 402, an elastomeric insulation layer is extruded onto one or more components of a power cable for an electric submersible pump (ESP), including at least a conductor. - At
block 404, an adhesive surface layer is created on the elastomeric insulation layer. - At
block 406, a fluoroplastic barrier layer is extruded onto the adhesive surface to molecularly cross-link with the elastomeric insulation layer. - The elastomeric insulation layer may be a cured ethylene propylene diene monomer (EPDM) rubber, and creating the adhesive surface layer may include activating a surface layer of the EPDM rubber with a plasma activation or an electron-beam activation.
- Creating the adhesive surface layer on the elastomeric insulation layer may further include extruding a fluoroplastic primer or adhesive onto the elastomeric insulation layer prior to extruding the fluoroplastic barrier layer.
- The
method 400 may use a triple extrusion process or tandem extrusion processes. - The fluoroplastic barrier layer may be one of a polyvinylidene fluoride fluoroplastic, a polyvinylidene difluoride (PVDF) fluoroplastic, a polyvinyl fluoride (PVF), an ethylene tetrafluoroethylene (ETFE), or a chlorotrifluoroethylene (CTFE). Alternatively the
barrier layer 210 may be selected from the polyaryletherketone family such as a polyetherketone (PEK), a polyether ether ketone (PEEK), or a polyetherketone-etherketoneketone (PEKEKK), etc. -
FIG. 5 is a flow diagram of anexample method 500 of making an ESP power cable. Operations of theexample method 500 are shown as individual blocks. - At
block 502, an elastomeric insulation layer comprising a fluoroplastic-compatible modified EPDM rubber is extruded onto one or more components of a power cable for an electric submersible pump (ESP), including at least a conductor. - At
block 504, the fluoroplastic-compatible modified EPDM rubber is preserved from an ambient environment; - At
block 506, a fluoroplastic barrier layer is extruded onto the fluoroplastic-compatible modified EPDM rubber. - At
block 508, an interface bonding surface is created between the fluoroplastic-compatible modified EPDM rubber of the elastomeric insulation layer and the fluoroplastic barrier surface. - The
method 500 may further include applying a fluoroplastic primer-adhesive as the interface bonding surface between the fluoroplastic-compatible modified EPDM rubber and the fluoroplastic barrier layer. The fluoroplastic primer-adhesive can be selected from the following: a synthetic rubber fluoropolymer elastomer, a terpolymer of tetrafluoroethylene (TFE) and vinylidene fluoride (VF2) and hexafluoropropylene (HFP), or a fluorothermoplastic of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride. - The
method 500 may further include adding an agent to the fluoroplastic primer-adhesive for stripping fluorine atoms from a face of the fluoroplastic barrier layer. When the fluoroplastic barrier layer is extruded to encapsulate the fluoroplastic-compatible modified EPDM rubber, the agent strips fluorine atoms from the face of the fluoroplastic barrier layer to allow molecular cross-linking between the fluoroplastic barrier layer and the fluoroplastic-compatible modified EPDM rubber. The agent may be a metal oxide and a dehydrohalogenating chemical, such as an onium compound, an organo-onium, an amidine, DBU, or DBN. - Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.
Claims (20)
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US15/323,695 US10181364B2 (en) | 2014-07-03 | 2015-06-19 | High reliability power cables for subsea application |
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US201462020888P | 2014-07-03 | 2014-07-03 | |
PCT/US2015/036722 WO2016003675A1 (en) | 2014-07-03 | 2015-06-19 | High reliability power cables for subsea application |
US15/323,695 US10181364B2 (en) | 2014-07-03 | 2015-06-19 | High reliability power cables for subsea application |
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US20170162296A1 true US20170162296A1 (en) | 2017-06-08 |
US10181364B2 US10181364B2 (en) | 2019-01-15 |
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CN105885150A (en) * | 2016-05-18 | 2016-08-24 | 无为县金华电缆材料有限公司 | High-temperature resistant environment-friendly cable rubber layer formula |
CN106084497A (en) * | 2016-06-20 | 2016-11-09 | 安徽海容电缆有限公司 | A kind of heat conduction cable material |
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US10181364B2 (en) | 2019-01-15 |
WO2016003675A1 (en) | 2016-01-07 |
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